The invention is directed to an apparatus and a method for acquiring the nature of a toner particle layer in a printer or copier. The toner particle layer is contained in the dielectric of a capacitor at least at times. Electrical properties of the capacitor can be used to draw conclusions about the nature of the dielectric and, thus, about the nature of the toner particle layer. The invention is also directed to an apparatus and a method for acquiring the moisture content of a carrier material in a printer or copier.
For generating a visible image in electrographic printer or copier devices, toner is applied on a carrier medium and fixed thereon. A latent charge image is generated on an image-generating medium, for example on a photoconductor, and is subsequently inked with toner. The toner image is subsequently transferred onto a carrier material and fixed thereon. The obtainable print quality is particularly dependent on the inking degree of the print or toner image and, thus, on the amount of colorant transferred on a recording medium, i.e. on the transferred toner. In, for example, the presentation of a solid area, rastered half-tone areas, lines, characters and the like, the inking degree must be kept within certain limits. The first inking degree of a print or toner image must therefore be measured and the quantity of colorant or toner to be applied must subsequently be set with the assistance of a regulating system in conformity with the measured result. The regulating event can also be repeated at certain time intervals according to the demands made of the print quality.
For example, surface regions are designationally inkedxe2x80x94these being referred to as print or toner marksxe2x80x94for determining the inking degree of print or toner images.
The determination of the inking degree of print or toner marks can be undertaken directly on a recording medium and/or an image-generating medium such as, for example, a photoconductor drum or an applicator element.
For achieving a required printing quality, the amount of toner applied in the inking of the latent charge image must be kept exactly within predetermined limits since, for example, an area to be inked black only appears as deep black when enough toner is applied. On the other hand, too much toner dare not be applied given, for example, thin lines lying close to one another since the lines otherwise bleed into one another.
For economical as well as ecological reasons, it is not meaningful or justifiable to apply more toner on the photoconductor for an area to be inked than is absolutely necessary orxe2x80x94expressed in other wordsxe2x80x94only as much toner as required for the respectively desired inking degree should always be applied insofar as possible. Optoelectrically functioning sensor systems are known for measuring the inking degree of print or toner images in the form of toner marks. Upon employment of such systems, a toner mark is irradiated with visible or infrared light. On the basis of different reflection and absorption properties of toner marks that are dependent on the amount of toner contained in the toner mark, the intensity of the reflected or transmitted light is measured by means of an optoelectrical sensor system and the inking degree is subsequently identified. The measured result of optoelectrically operating sensor systems for determining the inking degree of toner marks, however, is also dependent on the optical properties of the medium on which the toner mark is applied. Print image mismatches thus can already occur given employment of different paper grades. Similar print image mismatches can occur, for example, due to fluctuations in the photoconductor charges.
Further, the reflected or transmitted light quantity decreases only until the surface elements of the toner mark have been covered gap-free with toner. Given completely absorbent toner material, a multi-layer tonering of the toner mark that increases thereafter no longer leads to changes in the reflected/absorbed light quantity and, thus, of the electrical signal. Optoelectrical sensors can thus not detect a further increase in the layer thickness. Different reflection and absorption properties are also present given different toner brands and given toners with different colors. An optoelectrical sensor must therefore be specifically adapted to the toner respectively employed or to each colored toner. These adaptations are very time-consuming and cost-intensive. Optoelectrical sensor systems deliver only inadequate measured results for specific colored toners.
DE 196 43 611 A1 discloses a method and an apparatus for determining an inking degree of tonered areas in a printer or copier device. For determining the inking degree, measurement is carried out relative to a non-tonered carrier medium as well as relative to a toner mark using two capacitative sensors arranged transversely relative to the conveying direction of a carrier material. The layer thickness of the toner layer is identified from the two measured values. However, imprecise measured results are already obtained given slight adjustments imprecisions of the sensor and given a topical variation of the physical properties of the carrier medium, a high print quality being no longer assured as a result thereof. Further devices and methods for determining the inking degree are disclosed by U.S. Pat. Nos. 6,021,294, 5,987,269, 5,918,085, 5,694,223, 5,657,114, 5,500,716, 4,935,776, 4,860,924, 4,706,032 and 4,245,022.
An object of the invention is to specify a simply constructed, cost-beneficial apparatus and a method that is simple to implement and by means of which the nature of a toner particle layer is relatively precisely determined. Another object of the invention is to specify a simply constructed apparatus and a method that is simple to implement and with which the moisture content of a carrier material is determined in a simple way.
According to the invention, a nature of a toner particle layer in a printer or copier is acquired by arranging a first capacitor plate and a second capacitor plate next to one another and lying opposite at least one cooperating electrode to form a first capacitor and a second capacitor. A layer that contains toner particles is arranged in a region between the two capacitor plates and the cooperating electrode. The two capacitors are charged with voltages opposite one another in a first switch status. In a second switch status, the first and the second capacitor plates are electrically connected to one another and a remaining charge is determined after a charge compensation. Conclusions about the nature of the toner layer are drawn from the remaining charge.